The present invention relates generally to devices and methods for promoting blood circulation to the heart muscle. More particularly, the present invention relates to devices and methods for forming holes or channels in the walls of a heart chamber such as those created during a percutaneous myocardial revascularization (PMR) procedure.
Assuring that the heart muscle is adequately supplied with oxygen is critical to sustaining the life of a patient. To receive an adequate supply of oxygen, the heart muscle must be well perfused with blood. In a healthy heart, blood perfusion is accomplished with a system of blood vessels and capillaries. However, it is common for the blood vessels to become occluded (blocked) or stenotic (narrowed). A stenosis may be formed by an atheroma which is typically a harder, calcified substance which forms on the walls of a blood vessel.
Historically, individual stenotic lesions have been treated with a number of medical procedures including coronary bypass surgery, angioplasty, and atherectomy. Coronary bypass surgery typically involves utilizing vascular tissue from another part of the patient""s body to construct a shunt around the obstructed vessel. Angioplasty techniques such as percutaneous transluminal angioplasty (PTA) and percutaneous transluminal coronary angioplasty (PTCA) are relatively non-invasive methods of treating a stenotic lesion. These angioplasty techniques typically involve the use of a guidewire and a balloon catheter. In these procedures, a balloon catheter is advanced over a guidewire such that the balloon is positioned proximate a restriction in a diseased vessel. The balloon is then inflated and the restriction in the vessel is opened. A third technique which may be used to treat a stenotic lesion is atherectomy. During an atherectomy procedure, the stenotic lesion is mechanically cut or abraded away from the blood vessel wall.
Coronary by-pass, angioplasty, and atherectomy procedures have all been found effective in treating individual stenotic lesions in relatively large blood vessels. However, the heart muscle is perfused with blood through a network of small vessels and capillaries. In some cases, a large number of stenotic lesions may occur in a large number of locations throughout this network of small blood vessels and capillaries. The torturous path and small diameter of these blood vessels limit access to the stenotic lesions. The sheer number and small size of these stenotic lesions make techniques such as cardiovascular by-pass surgery, angioplasty, and atherectomy impractical.
When techniques which treat individual lesion are not practical a technique know as percutaneous myocardial revascularization (PMR) may be used to improve the oxygenation of the myocardial tissue. A PMR procedure generally involves the creation of holes, craters or channels directly into the myocardium of the heart. PMR was inspired in part by observations that reptilian heart muscles are supplied with oxygen primarily by blood perfusing directly from within heart chambers to the heart muscle. This contrasts with the human heart, which is supplied by coronary vessels receiving blood from the aorta. Positive clinical results have been demonstrated in human patients receiving PMR treatments. These results are believed to be caused in part by blood flowing within a heart chamber through channels in myocardial tissue formed by PMR. Increased blood flow to the myocardium is also believed to be caused in part by the healing response to wound formation. Specifically, the formation of new blood vessels is believed to occur in response to the newly created wound. This response is sometimes referred to as angiogenisis. In addition to promoting increased blood flow, it is also believed that PMR improves a patient""s condition through denervation. Denervation is the elimination of nerves. The creation of wounds during a PMR procedure results in the elimination of nerve endings which were previously sending pain signals to the brain as a result of hibernating tissue.
The present invention relates generally to devices and methods for promoting blood circulation to the heart muscle. More particularly, the present invention relates to devices and methods for forming holes or channels in the walls of a heart chamber such as those created during a percutaneous myocardial revascularization (PMR) procedure. One embodiment of a catheter in accordance with the present invention includes an elongate shaft comprising a sheath disposed about an elongate shaft. The elongate shaft includes a distal end and a proximate end. The catheter also includes a distal port defined by an electrode disposed proximate the distal end of the elongate shaft.
A hub is disposed about the elongate shaft and the sheath proximate the proximal end of the catheter. The hub includes a proximal port, a connector, and a strain relief. The proximal port may be utilized to couple the catheter to a fluid source. In a presently preferred embodiment, the elongate shaft defines a lumen which is in fluid communication with the proximal port and the distal port of the catheter. A connector may be utilized to couple the catheter to an energy source. In a presently preferred embodiment the connector includes a connector pin which is electrically coupled to electrode.
A PMR system in accordance with the present invention may include a tube fitting adapted to couple with the proximal port of the catheter. The proximal port may be utilized to couple the catheter to a fluid source. The lumen of the elongate shaft is sealed proximate the proximal end of the elongate shaft. Fluid from a fluid source may enter the lumen of the elongate shaft via an aperture and exit via the distal port of the catheter.
In a presently preferred embodiment, the hub defines a connector lumen and the elongate shaft extends into the connector lumen forming a connector pin. In a presently preferred embodiment, connector pin is electrically coupled to the electrode of the catheter via the elongate shaft. A PMR system in accordance with the present invention may include a mating connector which is adapted to couple with the connector of the catheter. When a connector and mating connector are mated, an electrically connection may be formed between a lead wire and the connector pin.
The electrode may comprise a tip member which is fixed to the distal end of the elongate shaft. In a presently preferred embodiment, the tip member defines a tip lumen which is in fluid communication with the lumen of the elongate shaft. A coil comprising a plurality of turns is disposed about a portion of the elongate shaft. The coil is fixed to the tip member proximate a distal end thereof. The sheath may be disposed about the coil and elongate shaft.
An additional embodiment of a catheter in accordance with the present invention may include an elongate shaft comprising a sheath disposed about a coil comprising a plurality of turns, a lumen, and a wire disposed in the lumen. A hub assembly may be disposed about the elongate shaft assembly proximate the proximal end thereof. In a presently preferred embodiment, the hub assembly includes a strain relief and a positioning mechanism. The positioning mechanism includes a slider which is disposed in sliding engagement with a guiding surface defined by a hub of the hub assembly. The slider is coupled to the wire proximate a proximal end thereof. The slider may be moved from a first position to a second position. The slider may also be positioned at points between the first position and the second position.
In a presently preferred embodiment, the wire is held in tension when the slider is disposed in the first position. Also in a presently preferred embodiment, the wire includes a curved portion (not shown) proximate the distal end thereof. In this presently preferred embodiment, the curved portion of the wire is biased to assume a generally curved shape. The wire may be held in tension by the positioning mechanism. When the wire is held in tension adjacent turns of the coil may be urged into close proximity with each other, and the wire may be pulled straight (more or less). When the slider is in placed in the second position B the curved portion of wire is free to return to its unbiased, substantially curved shape.